Endwall film cooling can be greatly improved if the leakage coolant flow from the upstream gap between the combustor and vane endwall is effectively engaged. In this study, such a full coverage film cooling design, called axial-row configuration, is considered and the performance is studied by measuring the film cooling effectiveness distribution using PSP technique. Experiments were performed in a blow-down wind tunnel cascade facility at the isentropic exit Mach number of 0.5 corresponding to inlet Reynolds number of 3.8 105, based on the axial chord. Passive turbulence grid was used to generate freestream turbulence level about 19 % with a length scale of 1.7 cm. The results are presented as two-dimensional film cooling effectiveness distributions on the endwall surface with pitchwise averaged distributions in the axial direction. The focus of this study is evaluating the effect of coolant-to-mainstream mass flow ratio (MFR) and density ratio (DR) on a particular endwall cooling design. Increasing coolant amount for the upstream leakage exhibited increased local adiabatic cooling effectiveness levels with relatively uniform coverage area. However, the passage cooling was not improved at highest coolant MFR = 1.5% rather indicated an optimum value of MFR = 1% based on better coolant coverage on the endwall surface. For density ratio effect, results indicated the best performance at DR = 1.5.